Five provinces in Thailand have been hit by 11 bombings in less than a day, authorities say.

At least four Thai nationals have been killed and about 36 others were injured, including 10 foreigners, according to Anurak Amornpetchsathaporn with the Ministry of Public Health.

No one has claimed responsibility for the blasts, and it's not clear if the bombings are connected.

Thai police say there's no evidence the attacks are related to international terrorism.

"These incidents are different from the usual terrorism acts. They are more local sabotage on certain locations and provinces," Deputy Police Spokesman Maj. Gen. Piyapan Pingmuang said at a news conference Friday.

Political unrest has in recent years roiled Thailand, resulting at times in protests. The series of blasts comes days before the first anniversary of the Erawan Shrine bombing, which killed 20 people, and five days after the country voted on a new constitution.Pingmuang said the explosions are not linked to the Erawan bombing.